1. Technical Field
The invention relates to a semiconductor device and a method of manufacturing a semiconductor device and it is a technique capable of being applied to a semiconductor device provided with a vertical transistor having, for example, a trench gate structure.
2. Related Art
As one type of semiconductor device, there is a semiconductor device having a vertical transistor. The vertical transistor is used for, for example, an element which controls a large current. As the vertical transistor, there is a transistor having a trench gate structure. The trench gate structure is a structure in which a concave portion is formed in a semiconductor substrate, a gate insulating film is formed on the side surface of the concave portion, and a gate electrode is then embedded in the concave portion.
In recent years, there have been structures where a termination trench is provided outside a trench gate when seen in a plan view in each of the structures (refer to, for example, Japanese Unexamined Patent Application Publication No. 2002-299618, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2007-528598, Japanese Unexamined Patent Application Publication No. 2012-19188, and Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2010-541289).
The structure described in Japanese Unexamined Patent Application Publication No. 2002-299618 is a structure in which a termination trench is formed to be shallower than a trench gate.
In Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2007-528598, it is described where a film structure of the insulating film formed on the side surface of a termination trench is different from a film structure of the gate insulating film. Specifically, an additional insulating film is deposited on the insulating film of the same layer as the gate insulating film at a lower portion of the side surface and the bottom surface of a trench gate and on the side surface and the bottom surface of the termination trench. Furthermore, the additional insulating film is not formed on the side facing a trench electrode, of an upper portion of the side surface of the termination trench.
The structure described in Japanese Unexamined Patent Application Publication No. 2012-19188 is a structure in which an insulating film on the bottom surface of a termination trench is made thinner than an insulating film on the bottom surface of a trench gate.
The structure described in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2010-541289 is a structure in which an insulating film on the bottom surface and the side surface of a termination trench is made thicker than an insulating film (including a gate insulating film) on the bottom surface and the side surface of a trench gate.